Neuroscientists are increasingly seeing the human brain as a series of modifiable brain circuits. As a result, a lot of money is being spent on the development of biotechnologies that manipulate brain networks. Psychiatric drugs, it would appear, are on the way out.

Vaughan says that the 'brain circuit' model of human cognition is nothing new, but the fact that neuroscience and medicine are now finally taking the hint and reorienting themselves to focus on identifying and altering brain circuits most certainly is. What's more — and what many don't realize — the direct stimulation of brain circuits by implanted devices is already happening.

Vaughan writes:

Big money has already been committed. The Obama White House has promised $3bn to develop technology to help identify brain circuits, while the National Institute of Mental Health has promised to move its seven-figure funding away from research into conditions such as schizophrenia and depression towards a system that looks at how brain networks contribute to difficulties that are shared across diagnoses. This project, given the unspectacular name Research Domain Criteria or the RDoCProject, is being cited as an eventual replacement for the diagnostic system used by current-day psychiatrists.

Perhaps more surprising for some is the explosion in deep brain stimulation procedures, where electrodes are implanted in the brains of patients to alter electronically the activity in specific neural circuits.Medtronic, just one of the manufacturers of these devices, claims that its stimulators have been used in more than 100,000 patients. Most of these involve well-tested and validated treatments for Parkinson's disease, but increasingly they are being trialled for a wider range of problems. Recent studies have examined direct brain stimulation for treating pain, epilepsy, eating disorders, addiction, controlling aggression, enhancing memory and for intervening in a range of other behavioural problems.

New technologies such as optogenetics suggest that even finer control of brain circuits may be possible. While deep brain stimulation involves stimulating the brain with electrical currents, optogenetics involves injecting neurons with a benign virus that contains the genetic information for light-sensitive proteins. The brain cells then become light sensitive themselves and their activity can be controlled with millisecond flashes of light sent through embedded fibre optic cables. Until now, this has only been demonstrated in animals but there are high hopes that it could lead to precisely controlled treatments in humans that intervene only in carefully selected brain circuits.

Vaughn predicts that this medical revolution will hit full swing in the next several decades. And indeed, optogenetics in particular is poised to make a huge impact, including the treatment of heart disease, paralysis and even diabetes. Scientists have even used it to change the behavior of mice.